Use of common ion affect in chemical phase-analysis has been studied, In order to avoid the dissolubility of wollastonite and tunstite from the solution of complex samples, 1 ml of 5% sodium silicate-0.5% sodium tungstate mixed solution was added into the leaching liquor coataining 8%alnminium chloride. This method was applied far the determination of fluorite in ores with satisfactory result.